T-Mobile is raising the price of their SIM Starter Kit by $5, bringing it up to $25, effective immediately. The price increase debuted simultaneously with a promotion offering customers a free line, which means that customers looking to bring their own device will be paying that extra $5. It's quite likely that a large number of free lines given away will end up being customers' own devices like old phones and unlocked tablets, so the small price bump allows the Un-carrier to cash in on the promotion to some degree. Of course, customers taking advantage of the promotion are more than welcome to buy a device if they wish to do so.
Each T-Mobile SIM Starter Kit comes with the SIM card itself, which is a nano SIM. The kit that's included in the package makes the card usable in devices that take a Micro SIM or regular-sized SIM card, but those with one of the oddball devices that have used Mini SIM cards over the years will have to find an adapter elsewhere. The SIM Starter Kit doesn't come with any other hardware and doesn't require an activation through T-Mobile as you simply have to purchase it, use an adapter if necessary, and pop the card into your device of choice. If that device is either a T-Mobile phone or an unlocked device with GSM capabilities and compatibility with T-Mobile's bands, service should start up without any issues. On some devices, you may have to configure an APN for T-Mobile in your wireless settings.
There is no indication that the price will go down after the promotional period is over, so this is likely a permanent price increase, just like the $5 jump on SIM Starter Kits that T-Mobile announced a year ago. The change affects subscribers looking to get their hands on both prepaid and postpaid SIM card kits, though prepaid customers can take advantage of another promotional offer that knocks $15 off the price, meaning those customers only have to pay $10 for their SIM Starter Kits. The discount promotion and the free line promotion are both running for a limited time, though T-Mobile has yet to reveal when they will end.